Punching and dimpling tool



L. WEBER PUNCHING AND DIMPLING TOOL Filed Jan. 4, 1944 FIGURE 2.

FlGLJRE 3.

INVENTOR.

LOUIS WEBER BY (@1171 (Adz L ATTO Patented Dec. 23, 1947 PUNCHING AND DIMPLING TOOL Louis Weber, White Marsh, Md, assignor to The Glenn L. Martin Company, Middle River, Md., a corporation ofMaryland Application January 4, 1944, Serial No. 516,939

This invention relates to a tool for dimpling sheet metal.

In the installation of fastening devices, it is necessary to punch a relatively large hole in a sheet of material and dimple the sheet around the edges of the hole to provide for the countersunk head usually employed i the ordinary type of flush mounted fastener. The problems in volved in a sheet metal operation for the purpose of dlmpling a sheet for a fastener are two-fold, one, to dimple the sheet without distorting the surface of the sheet, and two, in the interest of strength, it is necessary that the edges of the hole be prevented from cracking during the dimpling operation in which the material immediately adjacent the hole is flanged to form the dimple,

By this invention a tool is provided which is readily adapted and used in any conventional punch press.

Another object of the invention is the provision of a tool which will punch and dimple a hole to receive a fastener in a single operation.

A further object of the invention is the provision of a tool that will form a dimpled hole while maintaining the plane surface of the sheet undistorted.

Another object of the invention is the provision of a punching and dimpling tool having a removable and replacable pilot pin.

A further object of the invention is the provision of a dimpling tool which maintains the edges of the hole from cracking under the stress of the dimpling operation.

Further and other objects will become apparent from the description of the accompanying drawings which form a part of this disclosure and in which like numerals refer to like parts.

In the drawings:

Figures 1 to 3 show the cooperation of the parts of the dimpling tool in the successive steps of operation.

Figure 4 shows a modified form of the tool.

Figure 1 of the drawing illustrates the principal structural features of the dimpling tool. Member I is fixed in the movable head of the punch press and consists of a portion 2 having a hole 3 and conical or beveled surface 4 surrounding the hole to assist in controlling the form of the flanged dimple in the sheet. Collar -5 has a concave surface 6 which cooperates with surface 1 for reasons that will be subsequently described. Housing member or base 8 is adapted to be secured to the work table of the punch press. Cylindrical member 9 is restrained in housing 8 by the shoulders on portion ID with the outer end substantially 2 Claims. (Cl. 153--21) 2 flush with the end of the housing. Stem H extends into hole l2 so that member 9 may be forced downwardly into the cavity in member 8 against the action of spring I3. Cavity I2 is formed in a block I4 which is threaded into housing 8 and a screw driver slot I5 facilitates the assembly of the device.

Pilot pin IT is removably secured in member 9 so that it may be changed for a different size hole.

Sheet I8 is shown in Figure 1, in place on pilot pin H for the subsequent operation of the tool.

Figure 2 shows the parts of the tool in position relative to the metal sheet just prior to the dimpling operation. It should be noted that sheet it rests between member 9 and the end of portion 2 which upon further pressure of the press, clamps sheet 18 immediately adjacent the hole firmly against member 9. Continued pressure forces member 9 to compress spring 13. As memher 9 moves inwardly of housing 8, the sheet 18 continues to be held by the clamping action of the end of portion 2 and portion 9. At all times during the dimpling operation, the edges of the hole are clamped firmly between portion 2 and membar 9. The dimple is practically formed by the metal being clamped as described and this edge pulled downwardly away from the sheet to form the dimple. The under surface of the dimple is unsupported but surface 4 controls the upper surface contour of the dimple in which the part of the fastener rests.

As will be seen in Figure 3, the material is drawn down into the cavity in member 8 formed by the retraction of member 9 to form a dimple in the sheet IS. The upper surface of the dimple is formed by surface 4 of member 2 and the material around the hole is prevented from slipping or fracturing under the stress of the dimpling operation by the clamping action of the end of member 2 and member 9. In other words, as the material is flanged downwardly by the end of portion 2, the fractures caused by the stress of stretching the metal are prevented at their source, namely, the edge of the hole.

A further inspection of Figure 3 will show that the cooperating concave and convex surfaces 6 and l bend the material of the sheet immediately adjacent the area being dimpled a slight amount in a direction opposite the motion of the dimpling peen 2. This amount is calculated according to the spring-back of the metal being dimpled so that the tendency of the metal around the dimple to be distorted will be counteracted by the slight form imparted to the sheet by cooperating surfaces 6 and 1 in the direction opposite to the motion of the dimpling peen. The result will be perfect continuity of the plane sheet up to the edge of the dimple in the sheet.

The modification shown in Figure 4 is intended for punching and dimpling a sheet. Member 2 has dimple forming surface 4' surrounding hole 3' and is mounted on a base adapted to rest on the work table of a press. Collar 5' having a concave top 6 is secured by a set screw to member 2. The movable portion of the tool is secured in the head of the press by member I, which is secured to plug l4. Punch II is secured in plug [4' by a setscrew 19. Spring 13' urges pressure pad 9 outwardly of housing 8'. The pressure pad slides on member II and moves within housing 8', as described above, for the dimpling operation.

Pilot pin I6 is removably secured in the end portion H of member H. Portion ll forms a punch and cooperates with die member 2 to punch and dimple holes in a sheet in one operation.

A hole in a sheet and pilot pin 16 serve to locate the dimple. Punch I 7' is moved downwardly in the press and with the cooperation of the die portion 2, a hole is punched equal to the diameter of punch IT. The slug falls off pilot pin 16 and out hole 3', The punch continues to move downwardly until the edges of the hole are firmly clamped by the cooperation of parts 2 and 9', and the sheet material is drawn inwardly of housing 8. Surface 4 forms the outer surface of the dimple. The dimpling operation is the same as previously described with all the advantages, with the added feature of punching the hole for the fastener in the same set-up for dimpling.

It is to be understood that certain changes, alterations, modifications and substitutions can be made without departing from the spirit and scope of the appended claims.

I claim as my invention:

1. A punching and dimpling tool comprising a housing having an aperture formed in one end, a punch secured within the housing and extending beyond the end of the housing, a pressure pad surrounding said punch and adapted to slide thereon, spring means to maintain said pressure pad in an initial position with the outer end thereof substantially flush with the end of said housing, a die member having a bore formed therein adapted to cooperate with said punch, said die having a beveled surface surrounding said bore to control the form of the dimple, the surface of said die immediately adjacent said bore adapted to coo erate with said pressure pad to clamp the edge of the sheet around the hole being punched, against said pressure pad while said die and said pressure pad draw the sheet adjacent the aperture within said housing over the edge of the aperture to form a dimple.

2. A metal working tool comprising a housing having a slightly convex surface on one end, a circular aperture formed in said end, a cylindri cal. extension carried within said aperture and extending beyond the end of the housing, and adapted to extend through the metal to be worked at a rivet hole in said metal, a pressure pad mounted in said housing adjacent said cylindrical extension and adapted for sliding movement Within said aperture, spring means to maintain said pressure pad in an initial position with the outer end thereof substantially flush with the end of said housing, but which will permit the retraction of said pressure pad in the metal Working operation, a die member having a bore formed therein adapted to cooperate with said cylindrical extension, a beveled surface surrounding said bore providing a dimple forming surface, a collar having a concave surface extending around said die from the outer edge of said beveled surface, the surface of said die immediately adjacent said bore adapted to securely clamp the edge of a sheet to be worked around a hole to be dimpled against said pressure pad while said die and said pressure pad draw said sheet adjacent said hole within said housing over the edge of said circular aperture in said housing to form a dimple,

LOUIS WEBER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,530,000 Kauffman Mar. 17, 1925 2,288,378 Veit June 30, 1942 2,328,919 Merriman Sept. 7, 1943 FOREIGN PATENTS Number Country Date 155,204 Great Britain Jan. 12, 1922 511,106 Great Britain Aug. 14, 1939 

